It may be desirable to reduce the mass and rotational inertia of the crankshaft in a vehicle to increase the vehicle's efficiency. Further, the engine may be able to rotate at higher engine speeds when rotational inertia of the crankshaft is reduced. However, when the mass and rotational inertia of the crankshaft are reduced, fundamental design characteristics such as crankshaft balance and load capacity may be compromised. Furthermore, the crankshaft's ability to convert reciprocating forces from pistons and connecting rods into rotational forces may be diminished when the mass of the crankshaft is reduced. Consequently, the operational life cycle of a crankshaft may be reduced when crankshaft mass is reduced. Further, engine noise, vibration, and harshness (NVH) may also degrade when crankshaft mass is reduced.
A crankshaft for a V-6 engine is disclosed in U.S. Pat. No. 4,730,512. In particular, a crankshaft having a reduced number of counterweights is described. The crankshaft balance is purportedly maintained by adjusting positions of the remaining counterweights. The Inventor has recognized various shortcomings with the aforementioned crankshaft. For example, the alignment and distribution of the counterweights disclosed in U.S. Pat. No. 4,730,512 cannot be applied to other engine configurations such as inline or flat cylinder configurations.
As such, various example systems and approaches are described herein. In one example, a crankshaft for an engine is provided. The crankshaft including a central pin coupling a first and second counterweight, each counterweights being asymmetric with respect to a plane radially aligned with a central axis of the central pin and a rotational axis of the crankshaft. The central pin located between the first set of outer pins, a first outer pin of the first set of outer pins coupling a first pair of cheeks, and a second outer pin of the first set of outer pins coupling a second pair of cheeks.
In this way, the mass of a crankshaft may be reduced as compared to crankshafts having one or more counterweights corresponding to each engine cylinder. The described crankshaft may be particularly useful for inline engines because fundamental design characteristics may be maintained. For example, since the crankshaft is well balanced, the engine may be able to operate at higher speeds. Further, since crankshaft balance is achieved without reducing the mass of load bearing portions of the crankshaft, the crankshaft can handle loads that are similar to higher mass crankshafts. Consequently, a crankshaft with lower rotational inertia to increase engine and vehicle efficiency is provided. Additionally, crankshaft manufacturing cost can be reduced because the crankshaft is made with less material. Further, less machining may be required during crankshaft manufacturing.
This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter. Furthermore, the claimed subject matter is not limited to implementations that solve any or all disadvantages noted in any part of this disclosure.